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United States Patent |
5,107,061
|
Ou
,   et al.
|
April 21, 1992
|
Removal of organochlorides from hydrocarbon feed streams
Abstract
The present invention is directed to the removal of organochlorides from
hydrocarbon streams using highly crystalline molecular sieve material,
such as zeolites, and particularly zeolite X in a sodium form, and the
removal of organochlorides from hydrocarbon streams containing olefinic
compounds using such molecular sieves in combination with alumina for the
purpose of effecting a decomposition of the organochloride into a
corresponding unsaturated hydrocarbon molecule and a molecule of
hydrocarbon chloride wherein the hydrocarbon chloride is removed from the
hydrocarbon stream by being adsorbed onto the adsorbent of the highly
crystalline molecular sieve used alone, or in combination with alumina in
those instances where olefinic compounds are present in the hydrocarbon
stream, so that the unsaturated hydrocarbon molecule may be recovered from
the resultant hydrocarbon stream containing a reduced amount of
organochlorides.
Inventors:
|
Ou; John D. Y. (Houston, TX);
Rosenfeld; Daniel D. (Houston, TX)
|
Assignee:
|
Exxon Chemical Patents Inc. (Linden, NJ)
|
Appl. No.:
|
505816 |
Filed:
|
April 6, 1990 |
Current U.S. Class: |
585/823; 585/642; 585/820 |
Intern'l Class: |
C07C 007/12; C07C 007/13 |
Field of Search: |
585/641,642,820
|
References Cited
U.S. Patent Documents
3383430 | Jul., 1964 | Hutson, Jr. et al.
| |
3862900 | Jan., 1975 | Reusser.
| |
3864243 | Feb., 1975 | Reusser et al.
| |
4216345 | Aug., 1980 | Messina et al.
| |
4384159 | May., 1983 | Diesen et al. | 585/642.
|
4404118 | Sep., 1983 | Herskovits.
| |
4488953 | Dec., 1984 | Tang et al.
| |
4557921 | Dec., 1985 | Kirsch et al. | 423/488.
|
4665270 | May., 1987 | Brophy et al. | 585/642.
|
4719007 | Jan., 1988 | Johnson et al.
| |
4814527 | Mar., 1989 | Diesen | 585/642.
|
Foreign Patent Documents |
52-65194 | May., 1977 | JP | 502/64.
|
Other References
Journal of Applied Chemistry of USSR translation of Zhurnal Prikladnoi
Khimii, vol. 43, No. 11, Nov. 1970, pp. 2477-2480.
English Language Abstract of Japanese Patent JP/52-065,194, T. Tetsuo.
|
Primary Examiner: McFarlane; Anthony
Attorney, Agent or Firm: Russell; Linda K., Sherer; Edward F.
Claims
What is claimed is:
1. A process for purifying a hydrocarbon stream containing organochlorides,
said process comprising:
exposing a hydrocarbon stream comprising an organochloride to a material
selected from the group consisting of molecular sieve material, alumina
material, and combinations of molecular sieve material and alumina
material under conditions comprising a temperature within the range of
about 10.degree. C. to about 100.degree. C. effective to decompose said
organochloride into its unsaturated hydrocabon molecule and a molecule of
hydrogen chloride, and to absorb said molecule of hydrogen chloride so as
to result in a hydrocarbon stream which is substantially devoid of
hydrogen chloride.
2. The process as defined by claim 1, wherein said molecular sieve material
is selected from the group of crystalline molecular sieve material having
a pore size within the range of 5 Angstrom units to about 15 Angstrom
units.
3. The process as defined by claim 2, wherein said highly crystalline
molecular sieve material is selected from a group consisting of zeolites.
4. The process as defined by claim 4, wherein said zeolites are selected
from the group consisting of zeolite X, Y, A, and mordenite.
5. The process as defined by claim 4, wherein said zeolites are selected
from the group of cation-exchanged zeolites.
6. The process as defined by claim 5, wherein the cations in said
cation-exchanged zeolites are selected from the group consisting of alkali
metals and alkaline earth metals.
7. The process as defined by claim 6, wherein said
8. The process as defined by claim 7, wherein said type X zeolite is Na X
zeolite.
9. The process as defined by claim 8, wherein said hydrocarbon stream
comprising said organochloride comprises olefin compounds.
10. The process as defined by claim 9, wherein said material effective to
decompose said organochloride comprises a combination of said Na X zeolite
and said alumina.
11. The process as defined by claim 10, wherein said olefinic compounds are
selected from the group consisting of mono-olefins, polyolefins, linear
olefins, branched olefins, alpha olefins, and internal olefins.
12. The process as defined by claim 8, wherein said hydrocarbon stream
comprises hydrocarbons selected from the group consisting of aromatics,
paraffins and olefins.
13. The process as defined by claim 12, wherein said organochloride is
selected from the group consisting of primary alkyl chlorides, secondary
alkyl chlorides, tertiary alkyl chlorides, and allyl chlorides.
14. The process as defined by claim 13, wherein said organochloride is
selected from the group consisting of primary butyl chlorides, secondary
butyl chlorides and tertiary butyl chlorides.
15. The process as defined by claim 14, wherein said exposing comprises
dehydrohalogenating said primary butyl chlorides and said secondary butyl
chlorides over said Na X zeolite and decomposing said tertiary butyl
chlorides over said alumina.
16. The process as defined by claim 15, wherein said exposing comprises
subjecting said hydrocarbon stream to said Na X zeolite and said alumina
in series.
17. The process as defined by claim 16, further comprising recovering said
unsaturated hydrocarbon product stream from which said hydrogen chloride
has been removed.
18. The process as defined by claim 8, wherein said organochlorides are
selected from the group consisting of secondary butyl chlorides and
tertiary butyl chlorides.
19. The process as defined by claim 18, further comprising recovering said
unsaturated hydrocarbon molecule from a resultant hydrocarbon product
stream from which said hydrogen chloride has been removed.
20. The process as defined by claim 19, wherein said hydrocarbon stream
comprises said secondary butyl chlorides and said tertiary butyl chlorides
at levels up to about 0.2, and said resultant hydrocarbon product stream
comprises reduced amounts of said secondary butyl chlorides and said
tertiary butyl chlorides at levels below about 1 ppm.
21. The process as defined by claim 2, wherein said conditions comprise
temperatures within the range of about 10.degree. C. to about 100.degree.
C., and pressures within the range of about ambient to about 500 psi.
22. The process as defined by claim 2, wherein said temperatures are within
the range of ambient temperatures of 15.degree. C. to about 65.degree. C.
Description
Field of the Invention
The present invention relates to the removal of halogen and
halogen-containing molecules from a hydrocarbon stream. More particularly,
the present invention relates to the removal of chemically-combined
halogens, such as chlorine, and more specifically organochlorides, from
hydrocarbons. Specifically, the present invention is directed to the
removal of organochlorides from hydrocarbons using molecular sieves, as
well as removing organochlorides from hydrocarbon streams containing
olefinic compounds using a combination of molecular sieves and alumina.
Discussion of Background and Material Information
The removal of halogens, and particularly chemically-combined halogens,
such as organochlorides, from feedstreams is highly desirable in order to
prevent potential catalyst deactivation as well as equipment corrosion.
Typically, hydrocarbon products contain various amounts of halogens, such
as chlorines, in the form of, for example, chemically-combined halogens,
such as inorganically combined chlorides and organically combined
chlorides, i.e., organochlorides. The presence of organochlorides in
hydrocarbon streams typically results from the introduction of
organochlorides into the hydrocarbon streams during conventional processes
for producing and treating hydrocarbon products. In many instances, the
organochlorides may become a part of the hydrocarbon product during the
reaction of the hydrocarbon streams from which the hydrocarbon product is
produced, for example, because metal chloride catalysts may be used during
such reactions which have a tendency to introduce chlorine into the
product which is not otherwise removable by conventional techniques such
as washing, using water or a caustic.
As previously indicated, if chemically-combined chlorines, such as
organochlorides, are not removed from the hydrocarbon streams, the
presence of organochlorides in the resultant hydrocarbon products,
particularly gasoline or other fuels, can cause corrosion of processing
equipment and engine parts, as well as other deleterious effects.
U.S. Pat. No. 3,862,900, REUSSER, is directed to a method for treating
hydrocarbons containing chemically-combined chlorine by passing the
hydrocarbons through a bed of molecular sieves of effective pore size in
the range of about 7 Angstrom units to about 11 Angstrom units to remove
the chemically-combined chlorine and other impurities.
U.S. Pat. No. 3,864,243, REUSSER et al., is directed to a method for
treating hydrocarbons containing chemically-combined chlorine by passing
the hydrocarbons through high surface area, porous alumina at ambient
temperatures to remove the chemically-combined chlorine and other
impurities.
U.S. Pat. No. 4,719,007, JOHNSON et al., is directed to a process for
hydrotreating a hydrocarbonaceous carbon stock which involves first
contacting the hydrocarbonaceous charge stock in the presence of hydrogen
with a hydrogenation catalyst; then contacting the hydrotreating reaction
zone effluent with an aqueous scrubbing solution; followed by introducing
a resulting admixture of the reaction zone effluent and the aqueous
scrubbing solution into a separation zone to provide a hydrotreated
carbonaceous stream having trace quantities of hydrogenatable
hydrocarbonaceous compounds, and a spent aqueous stream; and then
contacting the hydrotreated hydrocarbonaceous stream with an adsorbent to
remove at least a portion of the trace quantities of hydrogenatable
hydrocarbonaceous compounds from the hydrotreated hydrocarbonaceous
stream. In so doing, JOHNSON et al., require at least three treatments,
including hydrogenation, caustic scrubbing, and adsorption in order to
remove halogenated compounds from proposed feedstreams.
U.S. Pat. No. 4,404,118, HERSKOVITS, discloses that molecular sieves, such
as zeolites, have been used to remove ethers, alcohols and/or water from
light liquid phase hydrocarbon streams, such as streams which are rich in
C.sub.4 hydrocarbons. Specifically, HERSKOVITS discloses the use of
zeolitic adsorbents for removing sulfur-containing compounds and/or
oxygenates from such hydrocarbon streams. In addition to sulfur-containing
compounds, including mercaptans and carbon disulfide, it is also disclosed
that such zeolitic adsorbents are useful to remove halogenated compounds
and nitrogenous compounds, as well as unsaturated hydrocarbons when
considered to be contaminants in other hydrocarbon streams. Therefore, the
disclosed use of zeolitic adsorbents extends to nitrogenous compounds,
unsaturated hydrocarbons, oxygenated hydrocarbonaceous compounds, water,
halogenated hydrocarbonaceous compounds, and sulfur-containing compounds
from a process stream. As more specifically disclosed by HERSKOVITS, the
zeolitic adsorbent is used to remove such compounds from a paraffinic
hydrocarbon having less than 7 carbon atoms per molecule, and an olefinic
hydrocarbon having less than 7 carbon atoms per molecule, such that the
compounds released by the adsorbent during regeneration become part of a
hydrogen-rich stream which is disclosed as being easily removed, for
example, by condensation.
U.S. Pat. No. 4,216,345, MESSINA et al., is directed to processes for
obtaining linear alkylbenzenes which contain a chlorine content of less
than 100 ppm. As disclosed, the process involves partial chlorination of
linear paraffins having from 9 to 15 carbon atoms per molecule; catalytic
alkylation of benzene using the resulting mixture of chlorinated and
unreacted paraffins; and fractionation by distillation, after separation
of the catalyst, of the alkylation products thus obtained and recycling
the unreacted paraffins recovered from the fractionation stage to the
partial chlorination stage. It is disclosed that at least a part of the
unreacted paraffins to be recycled to the partial chlorination stages are
submitted to a purification treatment with molecular sieves. As disclosed,
the recycled paraffins containing such impurities, are .passed through one
or more beds of molecular sieves. In general, fixed beds are used, and it
is disclosed that molecular sieves based on zeolites are particularly
useful, with specific molecular sieves of the type X and of the type Y
having a pore size varying between about 9 Angstrom units and 10 Angstrom
units being preferred.
U.S. Pat. No. 3,383,430, HUTSON, Jr. et al., is directed to the removal of
primary haloalkanes which are present in alkylate products as impurities,
by contacting the alkylate with a molecular sieve to selectively adsorb
the haloalkanes. It is disclosed that the primary haloalkanes can be
desorbed from the molecular sieve and recovered as a second high purity
product of the process.
U.S. Pat. No. 4,488,953, TANG et al., is directed to a process for the
purification of recycled paraffins in a mono-chlorination process which
involves the removal of polar compounds, such as phenol, substituted
phenols, amines and the like using an adsorption process which uses metal
oxides as the adsorbents.
Belgium Patent No. 762 502, CELANESE CORP., is directed to the purification
of hydrocarbons containing an organic chloride as an impurity which
involves passing the organic chloride-containing hydrocarbon at a
temperature of at least 50.degree. C. through a bed of solid dry particles
whose surface contains at least one material selected from the group
consisting of aluminum, magnesium, calcium, sodium and potassium. Although
such metal oxides were disclosed as being useful for this purpose, there
was no disclosure that zeolites, much less zeolites used alone or combined
with alumina, would be particularly suitable for this purpose.
Japanese Patent 61-051-009-A is directed to the purification of polybutene
by the removal of chlorinated polybutane using alumina.
SUMMARY OF THE PRESENT INVENTION
In general, the present invention is based on the discovery that molecular
sieves are capable of removing organochlorides from hydrocarbons. More
specifically, the present invention is based on the discovery that the
effectiveness of chloride removal from hydrocarbon streams containing
olefinic compounds is improved by the combined use of alumina and
molecular sieves.
In accordance with the present invention, molecular sieves used alone or in
combination with alumina function as a catalyst to first decompose the
organochloride molecule which may be present in the hydrocarbon stream
into a corresponding unsaturated hydrocarbon molecule, and a molecule of
hydrogen chloride; the chloride is then removed by the adsorbent which
adsorbs the hydrogen chloride. The unsaturated carbon, however, is not
adsorbed by either the zeolite or the alumina but passes through the
decomposition zone and may be recovered in the product stream.
In a preferred embodiment, the present invention is directed to the removal
of organochlorides from hydrocarbon streams containing olefinic substances
by subjecting the olefinic stream to a highly-crystalline molecular sieve
and alumina under conditions suitable for decomposing the organochloride
into its corresponding unsaturated hydrocarbon molecule and a molecule of
hydrogen chloride; adsorbing the hydrogen chloride; and recovering the
corresponding unsaturated hydrocarbon from the product stream.
BRIEF DESCRIPTION OF THE DRAWING
The Figure is a flow chart for the adsorption process the present invention
.
DETAILED DESCRIPTION OF THE INVENTION
The present invention involves removing chemically-combined halogens, such
as organochlorides, from hydrocarbon streams containing organochlorides,
by contacting the hydrocarbon stream containing organochlorides with
appropriate catalytic materials for a time and under conditions sufficient
to decompose the organochloride molecule into a corresponding unsaturated
hydrocarbon molecule and a molecule of hydrogen chloride which is then
adsorbed by a molecular sieve so as to effect chloride removal from the
hydrocarbon stream.
The present invention is also directed to removing organochlorides from a
hydrocarbon stream containing olefinic compounds and organochlorides by
contacting the hydrocarbon stream with a highly crystalline molecular
sieve material and alumina for a time and under conditions suitable for
decomposing the organochloride molecule into a corresponding unsaturated
hydrocarbon molecule and a molecule of hydrogen chloride. The hydrogen
chloride is then adsorbed by the molecular sieve material and alumina;
subsequently, the unsaturated hydrocarbon is recovered from the resultant
purified hydrocarbon stream.
For purposes of the present invention, molecular sieves having an effective
pore size of from about 5 Angstrom units to about 15 Angstrom units are
suitable; however, molecular sieves having an effective pore size within
the range of about 7 Angstrom units to about 10 Angstrom units are
preferred, with molecular sieves having an effective pore size within the
range of about 10 Angstrom units being more preferred. Highly crystalline
molecular sieves are preferred for removing organochlorides from
hydrocarbon streams, with zeolites being most preferred.
The zeolite preferred for purposes of the present invention has a pore size
within the range of about 5 Angstrom units to about 15 Angstrom units, and
may be in the form of crushed or beaded particles. For purposes of the
present invention include zeolite X, Y, A, beta and mordenite are the more
preferred zeolites. However, zeolite X, i.e., sodium X zeolite, is the
most preferred zeolite. Zeolite X molecular sieves are described in U.S.
Pat. No. 2,883,244, a specific example which is disclosed in U.S. Pat. No.
3,862,900, the disclosures of which are hereby incorporated by reference
herein thereto.
Properties of zeolites suitable for this application are described, for
example, in "Zeolite Molecular Sieves" by D. W. Breck, R. E. Krieger
Publishing Co., 1984. The zeolites are commercially available from UOP
Inc. Properties of some zeolites are listed below:
Zeolite X
Average composition: Na:.sub.2 O.multidot.Al.sub.2 O.sub.3
.multidot.2.5SiO.sub.2 .multidot.6H.sub.2 O
Pore Diameter: .about.10 A
Reference: R. M. Milton, U.S. Pat. No. 2,882,244 (1959)
Zeolite Y
Average composition: Na:.sub.2 O.multidot.Al.sub.2 O.sub.3
.multidot.4.8SiO.sub.2 .multidot.8.9H.sub.2 O
Pore Diameter .about.10 A
Reference: D. W. Breck, U.S. Pat. No. 3,130,007 (1964)
Zeolite A
Average composition: 0.25Na:.sub.2 O.multidot.0.75CaO Al.sub.0.2 O.sub.3
SiO.sub.2 4.5H.sub.2 O
Pore Diameter: .about.5 A
Reference: R. M. Milton, U.S. Pat. No. 2,882,243 (1959)
Zeolite Mordenite
Average composition: Na.sub.2 O.multidot.Al.sub.2 O.sub.3
.multidot.9-10SiO.sub.2 .multidot.6H.sub.2 O
Pore Diameter: .about.7 A
Reference: R. M. Milton, U.S. Pat. No. 2,882,244 (1959)
The present invention is also based on a discovery that, in the presence of
olefinic compounds, the effectiveness of chloride removal may be improved
by the combination of alumina with the molecular sieves. In this regard,
the removal efficiency has been discovered to be improved by combining
alumina adsorbent and zeolitic adsorbent in series or in a mixture.
Alumina suitable for purposes of the present invention may be selected from
conventional alumina adsorbents which have appropriate high adsorptive
power, a high surface area, suitable hardness, resistance to crumbling
during handling and use, suitable size and granular form. A representative
example of alumina suitable for purposes of the present invention is
disclosed in U.S. Pat. No. 3,864,243, the disclosure of which is hereby
incorporated by reference herein thereto. The following description
relates to alumina suitable for purposes of the present invention.
Kaiser Activated Alumina A-201 (neutral)
______________________________________
8 .times. 14 mesh spheres with a high surface area (325
______________________________________
m.sup.2 /gm)
Typical analysis 93.25% Al.sub.2 O.sub.3
(dry basis) 0.35% Na.sub.2 O
0.02% Fe.sub.2 O.sub.3
0.02% SiO.sub.2
______________________________________
In accordance with the present invention, alumina has been found to be
particularly effective in decomposing tertiary chlorides, while zeolite
has been used to dehydrohalogenate primary and secondary chlorides.
The hydrocarbon stream including the organochloride treated in accordance
with the present invention preferably includes olefin compounds, and the
material effective to decompose the organochloride is a combination of Na
X zeolite and said alumina. The olefinic compounds present in the
hydrocarbon stream are selected from the group consisting of mono-olefins,
polyolefins, linear olefins, branched olefins, alpha olefins and internal
olefins. The hydrocarbon stream treated in accordance with the present
invention may also include hydrocarbons selected from the group consisting
of aromatics and paraffins as well as olefins. The organochlorides removed
from the hydrocarbon stream in accordance with the present invention are
selected from the group consisting of primary alkyl chlorides, secondary
alkyl chlorides, tertiary alkyl chlorides, and allyl chlorides, and
preferably are selected from the group consisting of primary butyl
chlorides, secondary butyl chlorides and tertiary butyl chlorides.
In a preferred embodiment of the present invention, the step of exposing
the hydrocarbon stream to the previously described materials involves
dehydrohalogenating the primary butyl chlorides and the secondary butyl
chlorides over an Na X zeolite and decomposing the tertiary butyl
chlorides over alumina, preferably wherein the step involves subjecting
the hydrocarbon stream to the Na X zeolite and the alumina in series. The
process of the present invention also involves recovering the unsaturated
hydrocarbon product stream from which the hydrogen chloride has been
removed.
In another preferred embodiment, the organochlorides which are removed
preferably include secondary butyl chlorides and tertiary butyl chlorides,
and the process of the present invention also involves recovering the
unsaturated hydrocarbon molecule from a resultant hydrocarbon product
stream from which the hydrogen chloride has been removed, wherein the
hydrocarbon feed stream includes the secondary butyl chlorides and the
tertiary butyl chlorides at levels up to about 0.2%, and the resultant
hydrocarbon product stream includes reduced amounts of the secondary butyl
chlorides and the tertiary butyl chlorides at levels below about 1 ppm.
The process of the present invention is performed under conditions
including temperatures within the range of about 10.degree. C. to about
100.degree. C. and pressures within the range of about ambient to about
500 psi; preferably the temperatures are within the range of ambient
temperatures of 15.degree. C. to about 65.degree. C.
The hydrocarbon stream containing organochlorides treated in accordance
with the present invention may be produced or otherwise obtained from
conventional procedures. For example, streams of hydrocarbons that have
been found to contain organochlorides include paraffins from isomerization
processes, olefins from isomerization processes, olefins from
polymerization processes, and the like. Also, processes utilizing a
chloride-base catalyst to isomerize linear paraffins to branched paraffins
could produce a small amount of alkylchlorides in the product streams.
Chloride-base catalysts are also frequently used for olefin polymerization
processes such as polybutene process and polyisobutylene process.
Contaminants of organochlorides in the form of monomers or polymers have
been observed in the product streams.
The present invention is particularly suitable for removing organochlorides
from hydrocarbons containing olefinic compounds. The problem of removing
organochlorides from hydrocarbon streams containing olefinic compounds
occurs in the case of utilizing the raffinate stream for a polyisobutylene
(PIB) process. The process uses aluminum chloride to catalyze the
polymerization of isobutylene to PIB. In addition to isobutylene, the
charge stock to the reactor usually contains butene-1, butene-2 and
butanes. Ideally, the catalyst would only polymerize isobutylene and leave
other compounds unscathed. These compounds and unreacted isobutylene would
then separated from PIB by distillation and used for other applications.
However, the raffinate stream from the PIB distillation column is usually
contaminated with butyl chlorides due to reactions between aluminum
chloride and butenes, and such a raffinate stream contaminated with butyl
chlorides cannot, therefore, be used for productions of MTBE, butene-1,
butene-2, and the like.
In addition to the foregoing, the process of the present invention is
applicable removing organochlorides from hydrocarbons produced by other
conversion processes, such as isomerization, and polymerization, that
yield a hydrocarbon effluent containing chemically-combined chlorines,
such as organochlorides.
As previously discussed, the present invention is directed to the removal
of organically-combined chlorine, i.e., organochlorides, from hydrocarbon
streams containing organochlorides by subjecting the hydrocarbon stream to
appropriate catalytic materials for a time and under suitable conditions
effective to decompose the organochloride into its unsaturated hydrocarbon
molecule and a molecule of hydrogen chloride, the latter of which is then
adsorbed by an adsorbent effective for this purpose. For example, in
accordance with the present invention, a raffinate stream from PIB
distillation column, which typically contains 50% n-butane, 30% butene-1,
15% butene-2, 3% iso-butylene, 2% isobutane, 50-100 ppm secondary butyl
chloride, and 5-10 ppm tertiary butyl chloride, is introduced into an
adsorption column packed with zeolite adsorbent, such as zeolites X, Y,
beta, and mordenite, at a temperature ranging from ambient to about
100.degree. C., a pressure from ambient to about 500 psig, and a flow rate
from about 0.5 to about 5 LHSV (Liquid Hourly Space Velocity). The
adsorbent decomposes secondary butyl chloride into n-butene and hydrogen
chloride and the resultant n-butene is released from the adsorbent pores
and recovered in the column effluent. Hydrogen chloride, however, is
adsorbed by the adsorbent and eliminated from the stream. The removal
mechanism for tertiary butyl chloride is similar except that isobutylene
instead of n-butene is formed.
The single figure of the accompanying drawing, which is presented as a
representative example of the present invention for illustrative purposes
and is not meant to limit the present invention to the details shown and
described, is a flowsheet of the process for the removal of
organochlorides in accordance with the invention.
As shown, the charge stock (containing normal butenes, isobutylene,
butanes, and low level of butyl chlorides and polyisobutylene) to be
treated for chloride removal is the raffinate stream from the
fractionation tower 2 of a polyisobutylene unit 1. The stream is
introduced into the adsorption column 3, where it is contacted with the
adsorbent for the purpose of dehydrochlorinating the organochlorides and
adsorbing the resultant hydrogen chloride. The effluent from the
adsorption column, which contains less than 1 ppm chloride, can be used as
feed stock for a down-stream methyl tertiary butyl ether (MTBE) unit 4.
The present invention has been found to be particularly useful in removing
organochlorides present in the hydrocarbon stream in relatively small
amounts.
EXAMPLES
The following non-limiting examples are given by way of illustration of the
present invention.
EXAMPLE I
The following example is given to evidence that the organochloride present
in the hydrocarbon stream is first decomposed into a corresponding
unsaturated hydrocarbon molecule and a molecule of hydrogen chloride
wherein the hydrogen chloride is removed by adsorption onto the molecular
sieve and the unsaturated hydrocarbon molecule is recovered in the
effluent product stream.
Three zeolite adsorbents including sodium-X, calcium-X and barium-X were
tested for butyl chlorides removal. The feed solution was a mixture of
0.461% secondary butyl chloride, 0.036% tertiary butyl chloride, and
99.503% n-heptane. There were no butenes or isobutylene in the feed
solution. Ten grams of the feed solution were allowed to equilibrate with
2 grams of each adsorbent in sealed bottles at ambient temperature and
pressure for 18 hours. After the equilibration, GC analysis indicated that
the concentration of butyl chlorides was less than 1 ppm in all three
solutions. However, low levels of n-butenes (butene-1 and butene-2) and
isobutylene in the solutions were detected. Since there were no butenes
initially present in the systems, the presence of these compounds and the
disappearance of chlorides indicated the dehydrochlorination of butyl
chlorides and the subsequent adsorption of hydrogen chloride.
EXAMPLE II
The following example is given to show that the removal efficiency of the
adsorbent is improved by combining alumina adsorbent and zeolitic
adsorbent in series or in a mixture, particularly for the treatment of a
hydrocarbon stream containing primary, secondary and tertiary
organochlorides.
Static Test
Three Parr reactors were charged with the following feed:
______________________________________
FEED: 68% unsaturated butenes,
32% saturated butanes,
45 ppm sec-butylchloride and
18 ppm tertiary butylchloride.
______________________________________
(1) To one was also added formulated Na-X.
(2) To another was added a 1:1 mixture of Na-X and Alumina (A-201).
(3) To the third was added a 1:3 mixture of Na-X and Alumina (A-201).
Each was then heated to about 55.degree. C. for four hours.
Analysis of the supernatent liquid indicated that the combination of Na-X
and Alumina adsorbed more of the organochlorides present than did the Na-X
alone:
______________________________________
(1) (2) (3)
______________________________________
sec butylchloride
10 ppm 0.8 ppm 0.6 ppm
ter butylchloride
3 ppm 0.5 ppm 0.2 ppm
______________________________________
As indicated, this example also shows that alumina is effective in
decomposing the tertiary chlorides while the zeolite was effective to
dehydrohalogenate primary and secondary chlorides.
EXAMPLE III
The following example illustrates the adsorption/ chemisorption mechanism
resulting in the generation of unsaturated hydrocarbons and hydrogen
chlorides.
A break-through test was conducted to determine the capacity of sodium-X
zeolite for butyl chlorides removal. The adsorbent was a clay-bound
sodium-X zeolite obtained from U.O.P. Inc. It was ground to particles with
sizes ranging from 30 mesh to about 60 mesh and calcined at 400.degree. C.
prior to use. The adsorbent was then loaded into a 5 cc stainless steel
column.
A feed solution containing 90% n-heptane, 10% butene-1, 450 ppm secondary
butyl chloride, and 90 ppm tertiary butyl chloride was pumped through the
column at 65.degree. C., 300 psig, and a flow rate of 1.2 LHSV. Column
effluent was sampled periodically and analyzed for butyl chlorides and
hydrogen chloride. It was found that the concentration of butyl chlorides
in product was below 1 ppm until the total amount of butyl chlorides
pumped through the column reached 10.5% of the weight of the sodium-X
adsorbent. The concentration of hydrogen chloride in product before and
after breakthrough was below detection limit.
As indicated, the dynamic tests conducted at 65.degree. C. result in
capacities of about 10.5% for organochlorides in heptane.
It will also be appreciated by those of ordinary skill in the art that,
while the present invention has been described herein by reference to
particular means, methods and materials, the scope of the present
invention is not limited thereby and extends to any and all other means,
methods and materials suitable for practice of the present invention.
Therefore, although the present invention has been described with
reference to particular means, materials and embodiments, from the
foregoing description one skilled in the art can easily ascertain the
essential characteristics of the present invention, and various changes
and modifications may be made to various usages and conditions, without
departing from the spirit and scope of the invention as described in the
claims that follow.
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